Combustion efficiency of an internal combustion engine mainly depends quality of air-fuel mixture. Generating Swirl at the a) inlet manifold, b) cylinder head, c) top of the piston plays vital role in achieving the good thermodynamic efficiency. Swirl is generated in different forms like vortex, tumble flow, squish and turbulence. In spark ignition (SI) engines, swirling of the air-fuel mixture is achieved during suction stroke called induction swirl which is generated in the induction manifold or specially formed contours over the piston.
In compression ignition (CI) engines, swirling is achieved at the end of the compression stroke which is called as compression swirl generated in the cylinder head. Spherical swirl chambers are formed in the cylinder head where diesel fuel is injected. During the compression stroke, the compressed air is forced into the spherical swirl chamber causing the injected fuel to mix thoroughly to achieve effective combustion. The swirl caused by these techniques are local to the small region of the cylinder or cylinder head which accomplish little improvement in fuel efficiency while producing harmful emissions.
The heat loss to the cooling medium is more than useful work on the piston. More than a third of the total heat of the consumed fuel is lost to the cooling medium and cooling system accessories. The prior art efforts to prevent heat loss to the cooling medium have not yielded favorable results.
IC engines suffer from a major pitfall that more than a third of heat generated is transferred to the cylinder walls. During combustion process flame propagates abruptly in all directions and conducts huge amount of heat to the cooling medium through the cylinder walls. Low heat rejection (LHR) engines were developed during 1980s in which combustion chambers are coated with zirconium based ceramics to prevent heat loss to the surroundings up to 7%. In gasoline engines, use of ceramic materials results in overheating of the intake air, which leads to undesirable engine knock at high load operations. Because of these reasons, the research on LHR engines has been discontinued.